This invention relates to a method for use in processing an article, such as a reticle, a mask, or the like. It is to be noted here that such an article may not always comprise a substrate and a surface layer, although description will be mainly restricted to an article comprising both a substrate and a surface layer. In addition, it is assumed that such a surface layer underlies a resist film which is unpatterned or patterned, although the surface layer may not always underlie any resist film. For brevity of description, it is further assumed that the surface layer comprises an unpatterned layer underlying an unpatterned resist film which is preliminarily subjected to exposure to form a latent image therein after deposition of the unpatterned layer on the substrate. Such an article comprising an unpatterned resist film will be referred to as an unpatterned article.
A conventional method serves to process an unpatterned article comprising an unpatterned surface layer and an unpatterned resist film. The unpatterned resist film is exposed in a pre-processing step so that a predetermined pattern is formed as a latent image in the unpatterned resist film. The unpatterned resist film mentioned above is developed in a developing step to form a patterned resist film on the unpatterned surface layer.
Subsequently, washing, rinsing, and drying steps are successively carried out as a processing step in relation to the patterned resist film attached to the substrate. During the processing step for the resist film, various sorts of solvents must be used to selectively remove the unpatterned resist film to leave the latent image and to thereby form the patterned resist film.
Thereafter, the unpatterned surface layer is selectively etched through the patterned resist film to render the unpatterned surface layer into a patterned surface layer. After formation to the patterned surface layer, the patterned resist film is removed and washed out. Subsequently, such washing and rinsing steps are followed by a drying step. Thus, the etching, the removing, the washing out, and the drying steps are carried out to leave the patterned surface layer on the substrate after the pre-processing and may be collectively called a patterning step.
During the removing step, the patterned resist film is removed by making use of a plurality of solvents. Specifically, a selected one of a solution of oxidizing agent, an organic solvent, and an oxygenic plasma may be used to remove the patterned resist film in the removing step. At any rate, a great amount of each solvent must be used to completely remove the patterned resist film. In addition, the oxidizing agent is liable to damage the substrate while the patterned resist film is not readily removed by the organic solvent. In addition, use of the oxygenic plasma results in pollution of the substrate because undesired materials, such as metal, are attached to the substrate.
As regards the washing out step, use of a liquidized or a supercritical gas has been disclosed in Japanese Unexamined Patent Publication No. 192333/1985 (Tokkai Syo 60-192333). In this event, a patterned surface layer is positioned into a pressure vessel or chamber with a substrate and is kept in a liquidized or a supercritical gas during a predetermined interval of time. After lapse of the predetermined interval, the pressure is rapidly decreased in the pressure chamber. The resultant gas is rapidly expanded, which brings about removal of the resist film remaining on the substrate, as clearly pointed out in the above-referenced publication. However, it has been found that such rapid expansion of the liquidized or the supercritical gas gives rise to damage of the substrate.
In any event, the washing and the rinsing steps must be repeated in the processing and the patterning steps. Therefore, the conventional method is troublesome and takes a long time.